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Discussion Starter #1
Hello,

Is it possible to have the furnace turn on whenever the HRV is set to max only? instead of having the furnace fan run all the time.
 

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Anything's possible. You would probably need a relay and transformer... maybe an air flow paddle switch in some situations. Depends on what type of HRV you have and how it switches speeds. More info needed to give more specific instructions. Generally any furnace blower can be easily controlled with a simple spdt relay that sources power from the furnace itself.
 
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Yep, that relay will keep the new fan control circuit from back feeding the thermostat and causing the compressor to kick on.

One issue with that relay is the loud click it makes. If you can hear that from your bedroom, you might want to select something quieter... like an ice cube type or even a solid state one. There are some standard one available with a noise rating <21 dBa so shop around if that's going to be an issue.
 

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Discussion Starter #5
The click is not an issue.
It's the furnace fan running all the time while the HRV is set to low is my issue. Makes the house feel drafty in between heat cycles.
 

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Sorry, I wasn't ignoring you... got called away. I took a look at the diagram for your unit and it looks like that furnace control is an optional feature. You would likely have been made aware of that when they installed it, assuming you were the initial buyer.

That actually makes it somewhat easier to install a control system that only engages the furnace blower when the HRV is in high mode.

But first consider just unplugging the optional furnace blower control system and never have the blower come on by HRV control. That must be an acceptable mode since that control is an optional feature... implies it will work without it. If that's not acceptable, read on:

You would need to install a current sensing switch on the high speed wire of the HRV unit's motor. Then run a 2 cond. wire from that and cut and connect it in series with one of the control coil feed wires (either one, doesn't matter which) going to the that optional furnace control relay's coil (#1 or #3 terminal). That will stop the relay from energizing until the HRV goes into high speed mode.
 
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You want the furnace fan to come on with the HRV, not the furnace itself, right? Why not just set the furnace to not have the fan on all the time.
 

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You want the furnace fan to come on with the HRV, not the furnace itself, right? Why not just set the furnace to not have the fan on all the time.
He was wanting the HRV to only turn on the furnace blower when the HRV was operating in HIGH mode. It has low-med-high speeds and is originally wired to turn the furnace blower on any time the HRV is on, regardless of what speed it is running at.

I think it's a good application for a current sensing switch.
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Discussion Starter #9
Thanks you guys are awesome!

Bear with me, I just need to splice # 3 wire the high speed lead from the motor? Sounds simple enough.

What colour is the high speed lead on the motor?
 

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From the schematic for your unit, the ORANGE wire is the high speed winding lead. For reference purposes, it lies between the gray and the green on that 6-pin Molex connector.

It shouldn't be much of a job if you are the least bit handy making electrical connections using squeeze connectors.
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Just so you're clear, the orange wire does not actually connect to the current switch, it just runs through the hole on the device. The actual switch contacts connect in series with the wire that's on the #3 lug of the relay pictured. And be sure to get a normally open current switch. I think you understood all that but want to be certain. Do not work on anything live... turn off the power at the breaker.
 
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Discussion Starter #12
I'm ok doing the squeeze connectors.

My configuration has the #3 relay terminal going to pin # 5 on the molex plug and #1 relay terminal going to pin # 7 on the molex plug.

Do I leave those alone ? and do I just splice the ORANGE wire with the wire between # 3 relay terminal and pin # 5 on the molex?

I know I sound dense, I need it to dumbed down to my level. I don't want to ruin any equipment in the house. My better half would kill me.

I greatly appreciate the help guys.
 

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No, you don't splice the orange wire into anything. That's line voltage and would fry the class 2 circuit!!! It just has to be rerouted to run through the hole on the current sensing switch that you will have to supply. See my previous post that was apparently made while you were typing.

I don't want you to risk your equipment if you don't fully understand the concept and process of what I have described. Call an electrician if you have any doubts.
 
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The SZC23-NO-AL-CH would be my choice... your first two links point to that same one... although the price is different!! I have no way of assessing the quality of those units but they have the right qualifications as to electrical ratings for what you need.
 
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You'll be welcome back and also expected back to report your success so others may possibly benefit later when reading this thread.

As I stated, I can't be sure of the quality of those current detector switches you linked since the only ones I ever used were much more expensive. We used them to protect expensive 3-phase equipment from getting damaged due to single phasing when one phase goes off, so a couple hundred dollar item was justified. In your situation, if they fail, it won't cause any damage so not to worry.
 
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Yes, once you get it installed, you need to set it properly.

Start with the adjustment potentiometer set at the highest position (fully clockwise).

Turn the HRV system on to the high setting.

Rotate the current switch potentiometer counterclockwise slowly until the blower starts up and then a little bit more. It's not critical... estimate how much rotation counterclockwise is left and setting it onward to 1/4 of that amount should be OK.

Then set the HRV to the medium setting and verify that furnace blower stops.

That should do it.
 
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Discussion Starter #20
I went for it today.
As per your instruction I turned the screw clockwise but it just spins to no end. I do hear a clicking sound. The red nor the green lights don't light up.
Bad switch?
 
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